Responses of a Mediterranean soft bottom community to short-term (1993-1996) hydrological changes in the Rhone river.

The polychaete fauna of muddy bottoms off the Rhone delta (NW Mediterranean) was seasonally sampled at two sites at 70 m depth, from 1993 to 1996. During this period, five severe flood events occurred. A clustering analysis (distance coefficient of Whittaker) and three way fixed factor ANOVAs (site x season x year) showed strong year-to-year changes in species density and community structure, changes that masked seasonal variations.

Fluctuations of macrobenthic populations: a link between climate-driven river run-off and sole fishery yields in the Gulf of Lions.

The Rhone river is the most important input to the Mediterranean Sea, responsible for 50% of the primary productivity of the Gulf of Lions. A highly variable amount of 1-23×10 t year of terrestrial material is exported to the sea by the Rhone and stocked on the continental shelf for the most part. Soft-bottom communities off the Rhone delta were dominated by polychaetes both in species richness and abundance, and exhibited strong temporal fluctuations mainly related to flooding events.

[Thermal anomaly in waters of the Gulf of Marseilles during the summer of 1999. A partial explanation of the mortality of certain fixed invertebrates?].

During summer 1999, a massive mortality of attached benthic invertebrates was reported at several points along the French Mediterranean coast, east of the Rhône River. Such a wide geographical extension suggested the occurrence of a climatic anomaly as a direct or an indirect cause of this phenomenon. The systematic observations of surface water temperature (1 record/30 min) and vertical thermal structure from 0 to 55 m (semi-monthly frequency) performed by the service of observation of centre d'océanologie de Marseille since 1994 in the Gulf of Marseilles (northwestern Mediterranean) compared with historical data obtained for the summer periods (June till October) indicates a thermal anomaly during summer 1999.

[Toxic effect of four heavy metals on the growth of unicellular marine algae].

The growth inhibition of phytoplankton, resulting from Cd, Cu, Hg and Pb in sea water, has been studied on 18 monospecific strains belonging to different taxonomic groups. Data obtained pointed out that all species are very susceptible to Hg, and slightly to Pb. Effects of Cu and Cd vary with species, but Cu appears to be more toxic with dinoflagellates than with diatoms.